1. Field of the Invention
The present invention relates to a safety apparatus for a steer-by-wire and, more specifically, to a safety apparatus for a steer-by-wire that can ensure the safety of a steer-by-wire using a simple and compact structure and can be manufactured at a low cost.
2. Description of the Prior Art
A steer-by-wire (SBW) refers to an apparatus that controls steering using hydraulic pressure or auxiliary electric power only through an electric signal instead of a mechanical structure connecting the rotation of a steering wheel and the rotation of wheels.
The SBW generally includes a steering angle sensor on a steering input side thereof and a steering output sensor and a steering actuator on a steering output side thereof. The steering angle sensor detects a steering angle, the steering output sensor detects the rotation angle of a wheel, and the steering actuator generates an auxiliary power to rotate the wheel.
When a driver turns a steering wheel, the steering angle sensor detects the number of turns of the steering wheel to transmit the same to an electronic control unit (ECU), and the ECU controls the steering actuator, which can rotate the wheel, to generate steering output.
However, in the SBW system, fatal errors may be caused by a non-steerable state in which an electric signal is not provided due to a short circuit or a contact failure of a wire on a signal path through which steering is detected and transferred to an actuator, and thus a driver's steering intention is not correctly transferred to the wheel, or in which the steering actuator or the electronic control unit breaks down and malfunctions.
A backup clutch driving apparatus for a steer-by-wire is exemplified as an example of a safety apparatus for preventing such problems from arising.
FIG. 1 illustrates a backup clutch driving apparatus for a steer-by-wire according to the related art.
As illustrated in FIG. 1, the backup clutch driving apparatus for a steer-by-wire according to the related art includes a first column shaft 102, a second column shaft 104, an electromagnetic coil 106, an armature 108, an output-side hub 110, an armature hub 112, and a plate spring 114.
The armature hub 112 is secured to the first column shaft 102 connected to a steering wheel (not illustrated), and the plate spring 114 is connected to the armature hub 112.
The armature 108 is attached to the plate spring 114.
The output-side hub 110 is secured to the second column shaft 104 and surrounded by the electromagnetic coil 106.
When the steer-by-wire is operating normally, the first and second column shafts 102, 104 are mechanically separated from each other. Therefore, a driver's steering force which is transmitted to the first column shaft 102 is not mechanically transferred to the second column shaft 104.
However, when an error occurs in the steer-by-wire, a current is applied to the electromagnetic coil 106, thereby causing a magnetic field. The magnetic field attracts the armature 108 against the restoring force of the plate spring 114 so that the armature 108 is brought into contact with the output-side hub 110.
When the armature 108 is brought into contact with the output-side hub 110, the first and second column shafts 102, 104 are mechanically connected to each other and the driver's steering force is transmitted to wheels, thereby solving a fatal error caused by malfunction of the steer-by-wire.
However, the backup clutch driving apparatus for a steer-by-wire according to the related art has a complex structure, and the electromagnetic coil employed for the backup clutch driving apparatus for a steer-by-wire has limitations due to its small driving force in cases where a large driving force is required and its high production cost is a drawback.